1. Field of the Invention
The present invention relates to a body-weight adjusting device for optimum use in a seat suspension of vehicles.
2. Description of the Prior Art
It has been known that a seat of a vehicle, especially a driver's seat, which is provided with a seat suspension, should be capable of adjusting the height of the seat suitably to accommodate the wieght of an occupant sitting on the seat.
Hitherto, it has been known to provide a device satisfying such requirement, a typical one of which will be described with reference to FIG. 1 of the accompany-ing drawings. In FIG. 1, designations (1) and (2) refer to an upper frame and a lower frame, respectively, of a seat. The lower frame (2), which is formed substantially in a rectangular shape, can be made of a metal frame and has a substantially block U-shaped cross-section with the opening of the U turned inwardly. The upper frame (1) is basically formed in flat plate-like shape with both the lateral portions, or operationally required portions thereof, being bent downwardly, and is made of a metallic material having a configuration substantially coextensive with the lower frame (2). To the upper frame (1), a cushion member can be mounted, using what may be referred to as a "cushion pan" (not shown).
Interposed between the upper frame (1) and the lower frame (2) is a pair of X-shaped links (3) which constitutes a seat suspension and is of a well-known type comprising two links (4), (5) rotatably, pivotally supported by a pivot means (6) substantially centrally of each link. The upper end portion (5a) of each of the links (5) is rotatably fixed by a pivot means (7) to the upper frame (1) rearwardly of the links, whereas the lower end portion thereof (4b) is rotatably fixed by a pivot means (8) to the lower frame (2). The other lower end portion (5b) is slidably secured to the lower frame (2) by means of a roller (9) or the like so as to be movable forwardly and backwardly relative to the lower frame (2). The forwardly-located upper end portions (4a) of links (4) are coupled by means of a rod (10) extended therebetween, thereby supporting the forward portion of the upper frame (1) in a direction from the bottom of the seat. The rearwardly-located upper end portions (5a) are coupled by means of a frame member (11) to which a pair of tension springs (12) are each secured at one end thereof.
With reference to both FIG. 1 and FIG. 2, a bell crank (14) is rotatably fixed by pivot means (13), such as to the suspension facing surface of the upper frame (1), and has an arrangement whereby one end portion thereof is engaged with a nut (21) of an adjusting spindle (15), while the other end portion thereof is rotatably connected to one end of a tension bar (16) by means of pivot (17). The tension bar (16) is connected at the other end thereof to the center portion of an equalizer frame (18) by a pivot means (19) so as to be rotatable about the pivot means (19). The equalizer frame (18) is secured at both ends thereof to the other ends of the foregoing pair of tension springs (12) respectively. The adjusting spindle (15) consists of a rotaty shaft with a thread groove (20) partially formed thereon with the nut (21) being meshed with the thread groove (20).
Substantially at the center of thus-constructed seat, a shock absorber (22) is arranged such that the one end is rotatably fixed to the rear section of the lower frame (2) and the other end is rotatably fixed to the rod (10).
Now, Several drawbacks or disadvantages are found in the above-described conventional device:
(a) The springs (12) cannot be spaced apart from each other at a great distance. Consequently, the relatively closely spaced-apart springs (12) do not provide a stable adjustment of a seat suspension when a heavy weight load is applied to the seat. PA1 (b) For adjustment of the seat suspension to accommodate a heavy occupant, the adjusting spindle (15) has to be rotated manually at a quite number of times. For example, when it is desired to adjust the seat suspension against a variation in occupant's weight from 50 kg up to 100 kg, the adjusting spindle (15) requires approximately 16 full rotations. Furthermore, the rotation becomes more difficult as the adjustment proceeds close to 100 kg. Consequently, the operability is extremely poor. PA1 (c) The adjusting spindle (15) is not accessible when the door of the vehicle is closed.